Furnace apparatus



Mai-ch- 7, 1939; J. MIRRA 2,149,706

FURNACE APPARATUS Filed March 9, 1958 INVENTOR ATTORNEY Patented Mar. 7, 1939 UNITED STATES PATENT OFFECE Application March 9,

6 Claims.

This invention relates to improvements in furnace apparatus, and particularly to devices for automatically regulating the draft of a steam furnace.

It is primarily within the contemplation of my invention to enable forced or induced draft apparatus to be automatically set into operation within predetermined pressure limits in a furnace provided with conventional draft regulating means operable within other limits. And in this aspect of my invention it is a further object to permit an electrically operated blower to automatically replace the natural draft of the furnace without interrupting its operation.

Another object of this invention is to produce a balanced draft by means of suitable regulating devices actuated by the pressure within the furnace.

It is also within the contemplation of my invention to employ the apparatus thereof for effecting economy in fuel consumption.

And it is still another object to enable the foregoing objectives to be attained by a simple, inexpensive and readily adjustable device.

Other objects, features and advantages will appear from the drawing and the description hereinafter given.

Referring to the drawing,

Figure 1 is a perspective view of a furnace equipped with the apparatus constituting my invention, certain of the parts being shown by means of broken lines in their projected positions. 7

Figure 2 is a fragmentary vertical section taken substantially along line 2-2'of Figure l, and

Figure 3 is a plan view of the structure of Figure 2.

In the drawing, the furnace 5 is provided with aconventional steam pressure gauge 6, natural draft regulator 1 and forced draft regulator 8. The regulator I is mechanical in action and contains a conventional steam-actuated diaphragm having associated therewith a plunger 9 inoperative engagement with the lever It, said lever being pivotally supported at the fulcrum l I and having mounted thereon a movable weight I 2. The said regulator 8 is also steam actuated and is in effect a switch of the make-and-break type, the drawing showing a conventional rocker mercury tube 50 although other forms of conventional make-and-break switches adapted to be actuated by steam pressure may be employed within the scope of this invention. The furnace also contains a conventional draft door l3 swingably mounted at the hinges l4, and a conven- 1938, Serial No. 194,755

tional check door l5 pivotally mounted at [6. The terminal portion ll of lever II) has suitably attached thereto the chain IB which, in the form illustrated, is operatively mounted over the pulleys l9 and 2B and is attached to the 5 check door l5. The apparatus thus far described is of more or less conventional structure.

Preferably exteriorally disposed with respect to the furnace is the blower 2| the outlet portion 22 thereof communicating with the valve duct 23 which is suitably connected to the pipe 24 leading to the furnace 5. Swingably mounted upon the pivotal support 25 is the valve member 26 which, in its closed or inoperative position, obstructs the outlet 22, and in its lower or operative position opens said outlet for communication with the pipe 24, as shown in Figure 2. Suitably connected to the valve 26 at the said pivotal mounting thereof is the arm 21, positioned outside of the duct 23, said arm being preferably substantially in the plane of valve member 26 and being movable therewith. The terminal portion 28 of said arm has attached thereto the chain or flexible link 29 the opposite end of which is attached to the lever 30 pivoted at 3| of the bracket 32. Pivotally attached to said lever 30 at connection 33 is the lever 34 which is pivoted at its fulcrum 35, the opposite end 36 of the lever being in operative engagement with the lever 31 pivotally supported by the bracket 38. The forward end 39 of said lever 31 has attached thereto the chain or flexible link 40 which is suitably attached to the lug 4| of door l3. It will be observed that the lever 31 has movably mounted thereover an adjusting weight 46, the purpose and operation of which will be more fully hereinafter described. The terminal I! of lever ID has also attached thereto another chain 42 attached at 43 to the rear arm of lever 3'l,the drawing showing said link in operative engagement with the pulleys 44 and 45'. From the said regulator 8 extend the conductors 41 which are electrically connected to an outlet 48 and a motor 49 associated with the aforesaid blower 2|. In the operation of this device, the regulator 8 is operatively set for a predetermined pressure, and the weight, l2 associated with the regulator 1 is set for a slightly higher pressure. When the steam pressure within the furnace reaches a predetermined limit, the switch 50 of the regulator 8 will automatically close the circuit through the motor 49 to bring the blower 2| into operation. This results in a flow of air through. the duct 22 and pipe 24, thereby increasing the draft within the furnace and causing a consequent increase in pressure.

It will be noted that the weight 46 normally tends to keep the valve member 26 in its closed position, inasmuch as said weight causes the rear arm of lever 31 and the right arm of lever 34 to be depressed, and consequently the left arm of lever 34 and the entire lever 30 to be raised, thereby carrying with it the link 29, arm 2! and valve 26. By properly adjusting the weight 46, there can be just enough tension within link 29 to carry the valve 26 to its closed position, and yet to permit the air of the blower to force' it open to the position shown by the dotted lines in Figure 2 when the blower is brought into action, thereby allowing the air to be forced into the furnace.

In the position above described, with the valve 26 open, the forward arm of the leveri'l will be depressed, thereby causing a lowering of the link 4!) and a consequent closing and'sealing of the draft door l3 to keep air from either entering or leaving the furnace. It should be noted that at this time the regulator I is inoperative inasmuch as it 'is set for a higher pressure than the regulator 8,and if the furnace pressure is not up to the lower limit for regulator l, the weight 12 will depress the rear arm of the lever I6 and cause a consequent raising of the forward terminal I! thereof. When this occurs, there will be a slack in both of the chains I8 and 42, so that the check door l5 will, by its own Weight, pivotally swing about the axis I B to its closed position; and inasmuch as the chain 42 is not under tension, it can have no possible effect upon the draft door l3. It thus appears that when the blower 2| is in operation, the entire furnace is sealed, both at the draft door l3 and check door I5.

As soon as the upper limit of the pressure for regulator '8 is passed, the circuit through conductors 41 will automatically be opened by the switch means 50, thereby shutting off the blower 2|. This will obviously cause the valve 26 to rise to its closed position, inasmuch as the weight 45 will cause a lowering of the rear arm of lever 37, a consequent lowering of the right arm of lever 34 and raising of the left arm thereof, and a raising of the lever 30 and the arm 21 through the link 29. The position of the parts when this occurs is indicated by broken lines in Figure 1. If the pressure should again at this point suddenly decrease, the regulator 8 will again be brought into operation to cause the blower to function; but if the pressure should continue to rise until it reaches or exceeds the lower limit for the regulator l, the steam acting upon the diaphragm therein will cause the plunger 9 to be raised to lift the lever l0 against the action of weight 12. This will cause a lowering of terminal I! of lever 10, carrying with it the link I8 and causing the check door l5 to open.- As the said terminal ll moves downwardly, it also'creates a tension within the chain 42, thereby causing a force to be applied at point of lever3'l, to lift said lever against the action of weight 46, and cause a consequent lowering of chain 40 and draft door l3. This will obviously decrease the draft and tend to decrease the steam pressure. It should be noted that when lever 37 is raised, its only effect upon chain 29 is to cause it to slacken due to the lowering of lever 30, which cannot in any substantial way affect the operation of the device, particularly inasmuch as the blower 2| is not in operation.

More specifically, when the upper limit of regu-' lator 8 is exceeded, the blower stops and the valve 26 is raised to its closed position by the action of weight 46. In this condition no air passes into the furnace through duct 24; but'inasmuch as the draft door I3 is open and the check door I5 is closed, there is sufficient draft to keep combustion quite active. If the pressure continues to rise, terminal I! of the lever III will be lowered (due to the action of regulator l) and the rear arm of the lever 31 will consequently be raised, thereby closing the draft door l3 and opening the check door I5. Although this action may permit the lowering of valve 26, this will not adversely affect the operation of the regulating system, for even if air may be ableto pass through the stationary fan blades into the duct 24 and into the furnace (because of such lowering of valve 26) the amount of such infiltration need,

only be sufficient to sustain combustion within the furnace. It is obvious that the fan itself does not permit the absolutely free passage there- ,through of air in view of the intervening vanes,

and when this is considered together with the fact that the cross-sectional area of duct 24 is, in the preferred form of my invention, considerably less than the draft door opening, as is disclosed in the drawing, it becomes all the more apparent that the lowering of valve 26 under the aforesaid conditions will hardly begin to offset the combined effect of a closing of the draft door l3 and opening of the check door Hi.

When the pressure is sufiiciently reduced, the terminal ll of lever I 9 will rise, causing the closing of the check door I5 and an opening of the draft door 13 under the influence of weight 46. Should there be a still further decrease in pressure, the regulator 8 will'be brought into operation, causing the blower 2| 'to driveair into the furnace in the manner aforesaid, and thereby increase the steam pressure.

It is thus apparent that the apparatus constituting my invention is adapted to permit the furnace, to operate under natural draft in conventional manner, until a great demand is made upon the furnace,whereupon the forced draft is automatically put into operation to keep the pressure within predetermined limits. With this design, the blower is hence only employed intermittently, if and when necessary, thereby obviating the expense of continuous operation which would otherwise be necessary. And with the blower and natural draft mechanism supplementing each other, only such quantities of fuel will be consumed as will be necessary to meet predetermined pressure requirements,-an arrangement which obviously is conducive to fuel economy. Although superatmospheric or positive pressure means are hereinabove refered to, it is understood that sub-atmospheric or induced draft means may be employed in conjunction with this apparatus with equal effectiveness; and it is further understood that the various embodiments above described and shown in the drawing are illustrative of my invention and not employed by way of limitation, inasmuch as numerous changes and modifications may be made, within the scope of the appended claims, without departing from the spirit of this invention.

What I claim is:

1. A draft regulating apparatus for a steam furnace having a natural draft inlet, comprising a draft door operatively associated with the inlet, a check door, electrically operated air-propelling means operatively connected to the furnace at a portion thereof remote from said natural draft air inlet, a make-and-break switch electrically connected to said air-propelling means, switch-control means operatively associated with the furnace and the switch and set to actuate the switch within a predetermined furnace pressure range whereby the said air-propelling means is operatively actuated only within said range, natural draft regulator means operatively associated with the furnace and including a weighted lever balanced to be actuated only within a range of furnace pressures above the range for said air-propelling means, and a weighted draft door lever operably connected to the draft door and normally urging the door into an open position, said natural draft regulator lever being independently connected to the said check door and the draft door lever and being adapted, upon an operative movement thereof, to exert an opening effort on the check door and an effort on the draft door lever to permit closing of the draft door.

2. A draft regulating apparatus for a steam furnace having a natural draft inlet, comprising a draft door operatively associated with the inlet, a chack door, electrically operated air-propelling means operatively connected to the furnace at a portion thereof remote from said natural draft air inlet, a make-and-break switch electrically connected to said air-propelling means, switch-control means operatively associated with the furnace and the switch and set to actuate the switch within a predetermined furnace pressure range whereby the said airpropelling means is operatively actuated only within said range, natural draft regulator means operatively associated with the furnace and including a weighted lever balanced to be actuated only within a range of furnace pressures above the range for said air-propelling means, and a weighted draft door lever operably connected to the draft door and normally urging the door into an open position, said natural draft regulator lever having one terminal thereof connected by two independent cable means to said check door and the said draft door lever, whereby upon an operative movement of the natural draft regulator lever said cable means will exert an opening effort on the check door and an effort on the draft door to permit closing of the draft door.

3. A draft regulating apparatus for a steam furnace having a natural draft inlet, comprising a draft door operatively associated with the inlet, a check door, electrically operated air-propelling means operatively connected to the furnace at a portion thereof remote from said natural draft air inlet, a make-and-break switch electrically connected to said air-propelling means, switchcontrol means operatively associated with the furnace and the switch and set to actuate the switch within a predetermined furnace pressure range whereby the said air-propelling means is operatively actuated only within said range, natural draft regulator means operatively associated with the furnace and including a weighted lever balanced to be actuated only within a range of furnace pressures above the range for said air-propelling means, a weighted draft door lever operably connected to the draft door and normally urging the draft door into an openv position, cable means operably connecting the free arm of the natural draft regulator lever to the check door, and other cable means operably connecting the said free arm of the natural draft regulator lever to the weighted arm of the draft door lever, whereby an operative movement of the natural draft regulator lever under the influence of the furnace pressure will cause an opening of the check door and a closing of the draft door against the action of the weight on the draft door lever.

1. In combination with a furnace having a natural draft air inlet, a draft door associated with the inlet, electrically-operated air-propelling means, .a conduit operatively connecting the airpropelling means to the furnace at a portion thereof remote from said natural draft inlet, a valve within the conduit, and a weighted lever connected at opposite arms thereof to said valve and said draft door respectively, the weight on said lever exerting a closing effort on said valve and an opening effort on said door, the air-propelling means being adapted to cause the air driven thereby to open said valve against the action of said weight, thereby operatively moving said lever and closing said door, and natural draft regulator means operatively associated with the furnace and said weighted lever whereby the lever will be actuated to close the draft door upon a predetermined rise of steam pressure, a make-and-break switch electrically connected to said air-propelling means, switchcontrol means operatively associated with the furnace and the switch and set to actuate the switch within a predetermined furnace pressure range whereby the said air-propelling means is operatively actuated only within said range, the said natural draft regulator means being operatively set for a higher pressure range than the said switch control means.

5. In combination with a furnace having a natural draft air inlet, a draft door associated with the inlet, a blower, motor means to drive the blower, a conduit connecting the blower to the furnace, a valve within said conduit, an arm attached to the valve and extending exteriorally of the conduit, a weighted lever connected at one terminal thereof with the draft door and normally holding the door in its open position, a coacting lever operatively connected to the other terminal of said weighted lever, connecting means operatively joining the said valve arm to the said coacting lever, the weight on said weighted lever exerting a closing effort on said valve through said connecting means, the blower being adapted to cause the air driven thereby to open said valve against the action of said weight, thereby causing an operative movement of the weighted lever and a closing of the draft door.

6. A furnace according to claim 5 wherein the said connecting means joining the said valve arm to the said coacting lever comprises a connecting lever pivotally mounted in the region of one end thereof, and a chain attached to the opposite end of the connecting lever and to the said valve arm, the said coacting lever being pivotally attached to said connecting lever intermediate the ends thereof.

JAMES MIRRA. 

